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首页> 外文期刊>Chemistry: A European journal >Porphyrin Metalation at MgO Surfaces: A Spectroscopic and Quantum Mechanical Study on Complementary Model Systems
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Porphyrin Metalation at MgO Surfaces: A Spectroscopic and Quantum Mechanical Study on Complementary Model Systems

机译：MgO表面的卟啉金属化：互补模型系统的光谱和量子力学研究

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摘要

We show that both single-crystalline and nanostructured MgO surfaces convert free-base tetraphenyl porphyrin (2HTPP) into magnesium tetraphenyl porphyrin (MgTPP) at room temperature. The reaction can be viewed as an ion exchange between the two aminic protons of the 2HTPP molecule with a Mg2+ ion from the surface. The driving force for the reaction is the strong stability of the formed hydroxyl groups along the steps and at defects on the MgO surface. We have used an integrated characterization approach that includes UV/Vis diffuse reflectance measurements on nanostructured powders, X-ray photoelectron spectroscopic investigation of atomically clean MgO(100) single-crystalline thin films, and density functional theory (DFT) calculations on model systems. The DFT calculations demonstrate that MgTPP formation is strongly exothermic at the corners, edges and steps, but slightly endothermic on terrace sites. This agrees well with the UV/Vis diffuse reflectance, which upon adsorption of 2HTPP shows a decrease in the absorption band associated with corner and edge sites on MgO nanocube powders.
机译：我们显示单晶和纳米结构的MgO表面在室温下将游离碱四苯基卟啉（2HTPP）转换为四苯基镁卟啉（MgTPP）。该反应可以看作是2HTPP分子的两个氨基质子与表面Mg2 +离子之间的离子交换。该反应的驱动力是沿着步骤以及在MgO表面缺陷处形成的羟基的强稳定性。我们已经使用了一种集成的表征方法，包括对纳米结构粉末进行UV / Vis漫反射测量，对原子清洁的MgO（100）单晶薄膜进行X射线光电子能谱研究以及对模型系统进行密度泛函理论（DFT）计算。 DFT计算表明，MgTPP的形成在拐角，边缘和台阶处强烈放热，但在梯田部位略有吸热。这与UV / Vis漫反射率非常吻合，后者在2HTPP吸附后显示出与MgO纳米立方体粉末上的角和边缘位点相关的吸收带下降。

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